Human reproductive systems include primary reproductive organs, called gonads.
A male's gonads are his testes (also called "balls"). Testes have dual functions: they produce reproductive cells (sperm), and they secrete the sex hormone testosterone.
Your reproductive system also includes accessory reproductive organs: a system of ducts that store and carry sperm, and glands that line and empty into these ducts.
The penis has more than one purpose and more than one function. The role of the penis in the reproductive system is to distribute sperm. It's also an organ of excretion (you pee out of it). The penis has another important function: producing intense physical pleasure.
The top ("bead") of the penis is called the glans. This is the most sensitive part to touch.
The glans is covered by a retractable layer of skin called the foreskin.
Some boys are circumcised at birrh-which is when the foreskin is surgically removed. Circumcision is sometimes performed for religious reasons. In terms of appearance, it's considered fine to be circumcised or fine to be left intact.
The glans of an intact penis is reported to be more sensitive than the glans of a circumcised penis.
*- Circumcision Doctors now agree that there is no medical reason to circumcise every newborn baby boy, and more and more parents in the U.S. are choosing not to do the procedure.
For one thing, routine circumcision of infants is no longer advised for prevention of penis cancer. (Penis cancer? Don't worry, young boys don't get this.)
Neither is it considered necessary for prevention of infection. Keeping an intact penis
clean is easily accomplished by gently pulling back the foreskin and washing under and around it with soup and water. This prevents smegma, the white substance secreted by the
glans from getting trapped behind the foreskin and causing infection. There medial reasons for circumcision in some cases, though. It may be recommended if a guy's foreskin is uncomfortably tight or too big to be moved down over the glans.
Circumcision surgery is relatively simple and straightforward, and it need not be a cause of concern if it becomes necessary. However, it does require surgery for an older child or a man.
The rest of the penis is called the shaft. The structure of the penis and the blood flow to and from the tissue inside it (erectile tissue) allow the penis to become temporarily rigid at times. This is called having an erection. Boys get erections throughout their lives, starting when they are babies. However, erections take on new meaning during puberty (see page 11).
The testes hang down in a pouch of skin called the scrotum. One ball is called a testis.The scrotum is internally divided into two sacs: one for each testis. The testes-and -scrotum combo is often referred to as testicles.
A couple of months before the birth of a mate baby, his testes descend nto h, s scrotum. They drop down from his abdomen, where they are formed.
Sometimes a testis doesn't descend. It just stays up in the abdomen or only comes partway down. If you have an undescended testis or partly descended testis, make an appointment to talk to your doctor about it. He or she may recommend correcting this with hormone treatment or surgery.
OUTSTANDING DESIGN FEATURES
Sperm (more about them on page 11) are manufactured at a lower temperature than the internal temperature of the body. Air circulating around the scrotum keeps the testes cooler. Also, there's a heat-exchange setup in the blood vessels that supply the testes: a cooling system.
Compliments of Testosterone
1. Your penis, balls, and scrotum will grow and change.
2. You'll begin to grow pubic hair.
3. Additional hair will grow on your body, including in your armpits.
4. There will be changes in your sweat glands.
5. There'll be changes in your oil glands.
6. Your voice will change.
7. You'll grow taller.
8. You’ll grow more muscular.
9. You may grow facial hair.
10. You’ll have more erections.
11. You’ll begin to manufacture sperm; you'll ejaculate.
12. You may have stronger sexual feelings.
The scrotum is capable of relaxing and tightening up. When it's chilly out, it pulls the testes as close as possible to the body-where they can warm up. When it's hot out, the scrotum gets all soft and droopy so that the testes can kind of swing in the breeze-to cool off.
This design isn't just to keep the testes at the absolute optimum temperature for sperm formation. The testes are unprotected by muscle or bone. This is risky, considering how important they are. To make the best of the situation, the scrotum tightens when a guy feels fear, drawing his testes closer to his body, where they will be safer if there is a confrontation.
It can also tighten when a guy feels nervous, and it tightens during sex.
One testis is usually a little bit bigger than the other. Both are carefully located in the scrotum so that one hangs lower than the other, usually the left one. This way, they aren't in a position to crush each other as a guy goes about an active daily life-that involves running, for instance.
Hormones are part of a communication system called the endocrine system. They are chemicals secreted by various organs of the body, including the brain, heart, kidneys, liver, thyroid gland, and testes. Hormones act like tiny messengers, circulating through the bloodstream and giving signals to cells to make changes that affect everything from brain development to kidney function.
Even though hormones are carried by the blood throughout the entire body and reach all the body's tissues, hormones are very specific as to which cells they influence. Sex hormones are present in both males and females, and reproductive functions are largely controlled by them. Males and females share some of the same sex hormones.
The main male sex hormone is testosterone. It's secreted in the testes by Leycliq cells, which are located in connective-tissue spaces between the tubules where sperm are formed.
Testosterone is famous for contributing to a boy's attraction to action. It enables guys to have the energy and concentration to perform well in a variety of situations.
Testosterone triggers many of the changes associated with puberty. It tells a guy's reproductive (sex) organs how and when to develop.
Secondary sexual characteristics aren't directly involved in reproduction, but they make up the many differences between male and female bodies.
Testosterone influences the development of these characteristics. Among other things, it deepens the voice, increases lean muscle mass, cuts down on body fat, increases bone density and growth, and triggers the growth of facial hair.
It also increases sex drive (libido).
Excerpted from The Guy Book by Mavis Jukes. Copyright © 2002 by Mavis Jukes. Excerpted by permission of Crown Books for Young Readers, a division of Random House LLC. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.